Characterization and prevention of formation damage for fractured carbonate reservoir formations with low permeability

Stress sensitivity and water blocking in fractured carbonate reservoir formations with low permeability were determined as the main potential damage mechanisms during drilling and completion operations in the ancient buried hill Ordovician reservoirs in the Tarim Basin. Geological structure, lithology, porosity, permeability and mineral components all affect the potential for formation damage. The experimental results showed that the permeability loss was 83.8%-98.6% caused by stress sensitivity, and was 27.9%-48.1% caused by water blocking. Based on the experimental results, several main conclusions concerning stress sensitivity can be drawn as follows： the lower the core permeability and the smaller the core fracture width, the higher the stress sensitivity. Also, stress sensitivity results in lag effect for both permeability recovery and fracture closure. Aimed at the mechanisms of formation damage, a modified low-damage mixed metal hydroxide （MMH） drilling fluid system was developed, which was mainly composed of low-fluorescence shale control agent, filtration control agent, lowfluorescence lubricant and surfactant. The results of experimental evaluation and field test showed that the newly-developed drilling fluid and engineering techniques provided could dramatically increase the return permeability （over 85%） of core samples. This drilling fluid had such advantages as good rheological and lubricating properties, high temperature stability, and low filtration rate （API filtration less than 5 ml after aging at 120 ℃ for 4 hours）. Therefore, fractured carbonate formations with low permeability could be protected effectively when drilling with the newly-developed drilling fluid. Meanwhile, field test showed that both penetration rate and bore stability were improved and the soaking time of the drilling fluid with formation was sharply shortened, indicating that the modified MMH drilling fluid could meet the requirements of drilling engineering and geology.

Damage control surgery for severe pancreatic trauma

Pancreatic trauma as a challenge before and during explorative laparotomy is associated with multiple visceral injuries or critical conditions. Its optimal management remains controversial.The current concept of damage control surgery (DCS) has been increasingly accepted. DCS

Damage alarming of long-span suspension bridge based on GPS-RTK monitoring

Structure damage identification and alarming of long-span bridge were conducted with three-dimensional dynamic displacement data collected by GPS subsystem of health monitoring system on Runyang Suspension Bridge.First,the effects of temperature on the main girder spatial position coordinates were analyzed from the transverse,longitudinal and vertical directions of bridge,and the correlation regression models were built between temperature and the position coordinates of main girder in the longitudinal and vertical directions;then the alarming indices of coordinate residuals were conducted,and the mean-value control chart was applied to making statistical pattern identification for abnormal changes of girder dynamic coordinates;and finally,the structural damage alarming method of main girder was established.Analysis results show that temperature has remarkable correlation with position coordinates in the longitudinal and vertical directions of bridge,and has weak correlation with the transverse coordinates.The 3%abnormal change of the longitudinal coordinates and 5%abnormal change of the vertical ones caused by structural damage are respectively identified by the mean-value control chart method based on GPS dynamic monitoring data and hence the structural abnormalities state identification and damage alarming for main girder of long-span suspension bridge can be realized in multiple directions.

Medical aspects of terrorist bombings: A focus on damage control surgery and damage control resuscitation

Although terrorist bombings have tormented the world for a long time, currently they have reached unprecedented levels and become a continuous threat without borders, race or age. Almost all of them are caused by improvised explosive devices. The unpredictability of the terrorist bombings, leading to simultaneous generation of a large number of casualties and severe "multidimensional" blast trauma require a constant vigilance and preparedness of every hospital worldwide. Approximately 1.0%-2.6% of all trauma patients and 7% of the combat casualties require a massive blood transfusion. Coagulopathy is presented in 65% of them with mortality exceeding 50%. Damage control resuscitation is a novel approach, developed in the military practice for treatment of this subgroup of trauma patients. The comparison with the conventional approach revealed mortality reduction with 40%-74%, lower frequency of abdominal compartment syndrome(8% vs 16%), sepsis(9% vs 20%), multiorgan failure(16% vs 37%) and a significant reduction of resuscitation volumes, both crystalloids and blood products. Damage control surgery(DCS) and damage control resuscitation(DCR) are promising new approaches, contributing for the mortality reduction among the most severely wounded patients. Despite the lack of consensus about the optimal ratio of the blood products and the possible influence of the survival bias, we think that DCR carries survival benefit and recommend it in trauma patients with exsanguinating bleeding.

Formation damage control of high permeability sandstone reservoir

The concern on formation damage control of high permeability sandstone reservoir has been growing in oil industry in recent years. The invasion of particles and the filtrate of drilling fluid are proven as one of the key factors accounting for reservoir damage. Based on the ideal packing theory, the practical software has been developed to optimize the blending proportion of several bridging agents, and the core flooding tests were conducted to evaluate return permeability of core samples contaminated with different drilling fluids. Experimental results show that the ideal packing approach can reduce the dynamic filtration rate, improve the return permeability and drawdown the breakthrough pressure, indicating that this kind of drilling fluids can meet the demands of formation damage control for high permeability sandstone reservoirs. Some applying procedures for formation damage control are also proposed in this paper.

Surgical management of high-grade pancreatic injuries: Insights from a high-volume pancreaticobiliary specialty unit

BACKGROUND The management of high-grade pancreatic trauma is controversial.AIM To review our single-institution experience on the surgical management of blunt and penetrating pancreatic injuries.METHODS A retrospective review of records was performed on all patients undergoing surgical intervention for high-grade pancreatic injuries [American Association for the Surgery of Trauma(AAST) Grade Ⅲor greater] at the Royal North Shore Hospital in Sydney between January 2001 and December 2022. Morbidity and mortality outcomes were reviewed, and major diagnostic and operative challenges were identified.RESULTS Over a twenty-year period, 14 patients underwent pancreatic resection for highgrade injuries. Seven patients sustained AAST Grade Ⅲinjuries and 7 were classified as Grades Ⅳ or Ⅴ. Nine underwent distal pancreatectomy and 5 underwent pancreaticoduodenectomy(PD). Overall, there was a predominance of blunt aetiologies(11/14). Concomitant intra-abdominal injuries were observed in 11 patients and traumatic haemorrhage in 6 patients. Three patients developed clinically relevant pancreatic fistulas and there was one in-hospital mortality secondary to multi-organ failure. Among stable presentations, pancreatic ductal injuries were missed in two-thirds of cases(7/12) on initial computed tomography imaging and subsequently diagnosed on repeat imaging or endoscopic retrograde cholangiopancreatography. All patients who sustained complex pancreaticoduodenal trauma underwent PD without mortality. The management of pancreatic trauma is evolving. Our experience provides valuable and locally relevant insights into future management strategies.CONCLUSION We advocate that high-grade pancreatic trauma should be managed in high-volume hepatopancreato-biliary specialty surgical units. Pancreatic resections including PD may be indicated and safely performed with appropriate specialist surgical, gastroenterology, and interventional radiology support in tertiary centres.

Conservative management of multi-trauma induced peritonitis:Experience,outcomes,and indications

BACKGROUND The concept of mandatory laparotomy in treating traumatic peritonitis has been increasingly questioned recently.AIM To summarize and share the experience of conservative treatment of patients with multi-trauma induced peritonitis.METHODS A retrospective review was performed on patients with multiple injury induced traumatic peritonitis.RESULTS A total of 184 patients with multiple injury induced traumatic peritonitis were reviewed.46 of them underwent conservative treatment.None of the 46 patients with conservative treatment switched to surgical treatment,and all of them were cured and discharged after successful conservative treatment.No significant abnormal findings were observed at regular follow-up after discharge.CONCLUSION Conservative management is safe,effective,feasible,and beneficial in hemodynamically stable patients with traumatic peritonitis if there is no definite evidence of severe abdominal visceral organ injury.

Productivity effect and overuse of pesticide in crop production in China

Chinese farmers are often accused of overusing pesticides that play a crucial role in enhancing crop yield by reducing losses to crop pests. Pesticide overuse has caused a series of negative health and environmental externalities. This paper quantiifes the productivity effect and the optimal amount of pesticides in rice, cotton and maize production in China from the economic perspective. Using survey data col ected in 2012 and 2013, both Cobb-Douglas and Weibul damage control speciifcations are used to estimate the production function. Results show that pesticides have statistical y signiifcant pro-ductivity effect on crop yield. On the condition of Weibul damage control speciifcations, the marginal products of 1 kg of the active ingredients of pesticides for rice, cotton and maize are 71.06, 22.73 and 98.45 kg, respectively. However, 57, 64 and 17%of the actual amount of pesticides are overused for rice, cotton and maize, respectively. Moreover, the productivity effect of pesticides would be overestimated using Cobb-Douglas speciifcation without incorporating a damage control agent.

Treatment of a patient with obstructive jaundice and extrahepatic portal hypertension

BACKGROUND: Recurrence of inflammation in the extrahepatic bile duct can lead to bile duct stenosis' obstructive jaundice and cavernous transformation of the portal vein. The latter can develop into extrahepatic portal hypertension (PHT). It is difficult to establish the correct method for treating these conditions. METHODS: At another hospital, a 51-year-old man developed PHT as a result of endoscopic retrograde cholangiopancreatography and endoscopic nasobiliary drainage to relieve cholelithiasis and obstructive jaundice. We dealt with the biliary tract obstruction through percutaneous transhepatic cholangial drainage (PTCD), followed by selective devascularization and a shunt operation 2 weeks after the disappearance of jaundice. Three months after cholecystojejunostomy, there were no obvious changes around the bile duct. RESULT: The patient recovered uneventfully and was discharged 14 days after operation. CONCLUSION: For this patient, surgery in stages was the best choice. The most suitable method to decrease jaundice is PTCD.

Splenic artery trunk embolization reduces the surgical risk of liver transplantation

BACKGROUND： Portal hypertension is one of the most im- portant clinical conditions that cause intraoperative intensive hemorrhage in cirrhotic patients undergoing liver transplan- tation. Pre-transplant portal decompression may reduce the intraoperative bleeding during liver transplantation.

Key details of the duodenal-jejunal bypass in type 2 diabetes mellitus rats

AIM: To investigate which surgical techniques and perioperative regimens yielded the best survival rates for diabetic rats undergoing gastric bypass. METHODS: We performed Roux-en-Y gastric bypass with reserved gastric volume, a procedure in which gastrointestinal continuity was reestablished while excluding the entire duodenum and proximal jejunal loop. We observed the procedural success rate, long-term survival, and histopathological sequelae associated with a number of technical modifications. These included: use of anatomical markers to precisely identify Treitz's ligament; careful dissection along surgical planes; careful attention to the choice of regional transection sites; reconstruction using full-thickness anastomoses; use of a minimally invasive procedure with prohemostatic pretreatment and hemorrhage control; prevention of hypo-thermic damage; reduction in the length of the procedure; and accelerated surgical recovery using fast-track surgical modalities such as perioperative permissive underfeeding and goal-directed volume therapy. RESULTS: The series of modif ications we adopted reduced operation time from 110.02 ± 12.34 min to 78.39 ± 7.26 min (P < 0.01), and the procedural success rate increased from 43.3% (13/30) to 90% (18/20) (P < 0.01), with a long-term survival of 83.3% (15/18) (P < 0.01). CONCLUSION: Using a number of fast-track and damage control surgical techniques, we have successfully established a stable model of gastric bypass in diabetic rats.

Shaking table comparative test and associated study of a stepped wall-frame structure

A new structural system called a stepped wall-frame structure is proposed in this study to solve the bottom yielding problem of RC frames, which widely occurred during previous earthquakes such as thc Wcnchuan and Yushu earthquakes in China. A 1/5 scale ordinary RC frame model and a stepped wall-frame model were subjected to shake table motions together to study the seismic behavior of the new structural system. This paper presents the dynamic characteristics, the seismic responses and the failure and collapse mechanism of the two models under low, moderate and high intensity shaking. The test results and further analysis demonstrate that the seismic performance of stepped wall-frame structures is superior to ordinary RC frames in terms of the well-controlled deformation pattern and more uniformly distributed damage. The stepped wall can effectively suppress the bottom yielding mechanism, and is simple, economical and practical tbr engineering practice.

Indications for the surgical management of pancreatic trauma: An update

Pancreatic trauma is rare compared to other abdominal solid organ injuries,accounting for 0.2%-0.3% of all trauma patients. Moreover, this type of injury may frequently be overlooked or not readily appreciated on initial clinical examinations and investigations. The organ injury scale determines the severity of the trauma. Nonetheless, there are conflicting recommendations for the best strategy in severe cases. Overall, conservative management of induced severe traumatic pancreatitis is adequate. Modern imaging modalities such as ultrasound scanning and computed tomography scanning can detect injuries in fewer than 60% of patients. However, magnetic resonance cholangiopancreatography and endoscopic retrograde cholangiopancreatography(ERCP) have diagnostic accuracies approaching 90%-100%. Thus, management options include ERCP and stent placement or distal pancreatectomy in cases of complete gland transection and wide drainage only for damage control surgery, which can prevent mortality but increases the risk of morbidity. In the majority of cases, surgical intervention is not required and should be reserved for only severe grade Ⅲ to grade Ⅴ injuries.

Mechanics of rib spalling of high coal walls under fully-mechanized mining

In order to solve the problem of rib spalling of high coal walls in fully-mechanized（HCWFM）mines,we used the principle of damage mechanics to analyze coal wall rib spalling.The results show that coal wall rib spalling is,to a certain degree,a macro-performance of the development of micro-cracks.We built a mechanical model to simulate the damage to the front of coal walls,carried out theoretical calculations of the damage parameters,analyzed the effect of mining height,original cracks,seam strength,horizontal stress,vertical displacement of the coal walls and other parameters on coal wall rib spalling, which conform well with the results of our field measurements and numerical simulation.The key to control coal wall rib spalling is to control the development of cracks in coal walls.Accelerating the speed of advancing the working face,improving the setting load of support and the horizontal force of the guard board,strengthening coal walls and other technical measures can effectively reduce the degree of damage to the coal walls and control coal wall rib spalling at HCWFM faces.

Designing Drill-in Fluids by Using Ideal Packing Technique

Selecting bridging agents properly is a critical factor in designing non-damaging or low-damaging drill-in fluids. Historically, Abrams＇ rule has been used for this purpose. However, Abrams＇ rule only addresses the size of particle required to initiate a bridge. The rule does not give an optimum size nor an ideal packing sequence for minimizing fluid invasion and optimizing sealing. This paper elaborates an ideal packing approach to solving the sealing problem by sealing pores with different sizes, especially those large pores which usually make dominant contribution to permeability and thereby effectively preventing the solids and filtrate of drill-in fluids from invading into formations, compared with the conventionally used techniques. Practical software has been developed to optimize the blending proportion of several bridging agents, so as to achieve ideal packing effectiveness. The method and its use in selecting the best blending proportion of several bridging agents are also discussed in this paper. A carefully designed drill-in fluid by using the ideal packing technique （named the IPT fluid） for offshore drilling operations at the Weizhou Oilfield, Nanhai West Company, CNOOC is presented. The near 100% return permeabilities from the dynamic damage tests using reservoir cores demonstrated the excellent bridging effect provided by this drill-in fluid.

Open abdomen in trauma patients:a double-edged sword

The use of open abdomen(OA) as a technique in the treatment of exsanguinating trauma patients was first described in the mid-19 th century. Since the 1980 s, OA has become a relatively new and increasingly common strategy to manage massive trauma and abdominal catastrophes. OA has been proven to help reduce the mortality of trauma. Nevertheless, the OA method may be associated with terrible and devastating complications such as enteroatmospheric fistula(EAF). As a result, OA should not be overused, and attention should be given to critical care as well as special management. The temporary abdominal closure(TAC) technique after abbreviated laparotomy was used to improve wound healing and facilitate final fascial closure of OA. Negative pressure therapy(NPT) is the most commonly used TAC method.

Feasibility and safety of “bridging” pancreaticogastrostomy for pancreatic trauma in Landrace pigs

BACKGROUND In recent years,we created and employed a new anastomosis method,“bridging”pancreaticogastrostomy,to treat patients with extremely severe pancreatic injury.This surgery has advantages such as short length of surgery,low secondary trauma,rapid construction of shunts for pancreatic fluid,preventing second surgeries,and achieving good treatment outcomes in clinical practice.However,due to the limited number of clinical cases,there is a lack of strong evidence to support the feasibility and safety of this surgical procedure.Therefore,we carried out animal experiments to examine this procedure,which is reported here.AIM To examine the feasibility and safety of a new rapid method of pancreaticogastrostomy,“bridging”pancreaticogastrostomy.METHODS Ten Landrace pigs were randomized into the experimental and control groups,with five pigs in each group.“Bridging”pancreaticogastrostomy was performed in the experimental group,while routine mucosa-to-mucosa pancreaticogastrostomy was performed in the control group.After surgery,the general condition,amylase levels in drainage fluid on Days 1,3,5,and 7,fasting and 2-h postprandial blood glucose 6 mo after surgery,fasting,2-h postprandial peripheral blood insulin,and portal vein blood insulin 6 mo after surgery were assessed.Resurgery was carried out at 1 and 6 mo after the former one to examine the condition of the abdominal cavity and firmness and tightness of the pancreaticogastric anastomosis and pancreas.RESULTS After surgery,the general condition of the animals was good.One in the control group did not gain weight 6 mo after surgery,whereas significant weight gain was present in the others.There were significant differences on Days 1 and 3 after surgery between the two groups but no differences on Days 5 and 7.There were no differences in fasting and 2-h postprandial blood glucose and fasting and 2-h insulin values of postprandial peripheral blood and portal vein blood 6 mo after surgery between the two groups.One month after surgery,the sinus tract orifice/anastomosis was patent in the two groups.Six months after surgery,the sinus tract orifice/anastomosis was sealed,and pancreases in both groups presented with chronic pancreatitis.CONCLUSION“Bridging”pancreaticogastrostomy is a feasible and safe a means of damage control surgery during the early stage of pancreatic injury.

Structural formation and evolution mechanisms of fracture plugging zone

A coupled CFD-DEM method is used to simulate the formation process of fracture plugging zone.A photo-elastic system characterizing mesoscale force chain network developed by our own is used to model the pressure evolution in fracture plugging zone to reveal the evolution mechanism of the structure of fracture plugging zone.A theoretical basis is provided for improving the lost circulation control effect in fractured reservoirs and novel methods are proposed for selecting loss control materials and designing loss control formula.CFD-DEM simulation results show that bridging probability is the key factor determining the formation of fracture plugging zone and fracture plugging efficiency.Critical and absolute bridging concentrations are proposed as the key indexes for loss control formula design.With the increase of absolute bridging concentration,the governing factor of bridging is changed from material grain size to the combination of material grain size and friction force.Results of photo-elastic experiments show that mesoscale force chain network is the intrinsic factor affecting the evolution of pressure exerting on the fracture plugging zone and determines the macroscopic strength of fracture plugging zone.Performance parameters of loss control material affect the force chain network structure and the ratio of stronger force chain,and further impact the stability and strength of fracture plugging zone.Based on the study results,the loss control formula is optimized and new-type loss control material is designed.Laboratory experiments results show that the fracture plugging efficiency and strength is effectively improved.

Acute Care/Trauma Surgeon＇s role in obstetrical/ gynecologic emergencies (The OBCAT Alert)

BACKGROUND:Overwhelming hemorrhage or other intra-abdominal complications may be associated with obstetrical or gynecologic(OB/GYN) procedures and may require the surgical training of an Acute Care/Trauma Surgeon.The OB Critical Assessment Team(OBCAT Alert) was developed at our institution to facilitate a multidisciplinary response to complex OB/GYN cases.We sought to review and characterize the Acute Care/Trauma Surgeon's role in these cases.METHODS:We conducted a retrospective review of all emergency consults during an OB/GYN case at our institution from 2008 to 2015.An OBCAT is a hospital based alert system designed to immediately notify OB/GYN,anesthesiology,Acute Care/Trauma,the intensive care unit(ICU),and the blood bank of a potential emergency during an OB/GYN case.RESULTS:There were 7±3 OBCAT alerts/year.Seventeen patients required Acute Care/Trauma surgery intervention for hemorrhage.Thirteen patients required damage control packing during their hospitalization.Blood loss averaged 6.8±5.5 L and patients received a total of 21±14units during deliveries with hemorrhage.There were 17 other surgical interventions not related to hemorrhage;seven of these cases were related to adhesions or intestinal injury.Seven additional cases required evaluation post routine OB/GYN procedure;the most common reason was for severe wound complications.There were three deaths during this study period.CONCLUSION:Emergency OB/GYN cases are associated with high morbidity and may require damage control or other surgical techniques in cases of overwhelming hemorrhage.Acute Care/Trauma Surgeons have a key role in the treatment of these complex cases.

Genetically Engineered Corn Rootworm Resistance: Potential for Reduction of Human Health Effects From Pesticides

Objective and Methods Insecticide use, grower preferences regarding genetically engineered (GE) corn resistant to com rootworm (CRW), and the health effects of using various CRW insecticides (organophosphates, pyrethroids, fipronil and carbamates) are reviewed for current and future farm practices. Results Pest damage to corn has been reduced only one-third by insecticide applications. Health costs from insecticide use appear significant, but costs attributable to CRW control are not quantifiable from available data. Methods reducing health-related costs of insecticide-based CRW control should be evaluated. As a first step, organophosphate insecticide use has been reduced as they have high acute toxicity and risk of long-term neurological consequences. A second step is to use agents which more specifically target the CRW. Conclusion Whereas current insecticides may be poisonous to many species of insects, birds, mammals and humans, a protein derived from Bacillus thurigiensis and produced in plants via genetic modification can target the specific insect of CRW (Coleoptra), sparing other insect and non-insect species from injury.